When seeding crops such as corn it is desirable to plant the corn seeds in a furrow at a pre-determined constant distance from each other. To achieve this constant spacing singulating meters have been developed which dispense seeds one at a time from a hopper full of seeds to a furrow opener. The dispensing rate is correlated to speed of travel over the field such that seeds land in the furrow at a constant spacing distance from each other. In a conventional corn planter, a plurality of row units is attached to a tool bar and each row unit plants one row of seeds. Each row unit has a seed hopper and a singulating meter dispensing seeds one at a time through a seed tube to a furrow made by a furrow opener mounted on the bottom of a furrow opener assembly. Such a corn planter is disclosed for example in U.S. Pat. No. 6,082,275 to Schaffert.
Most of these row units place the singulating meter as close as reasonably possible to the furrow to minimize the distance the seed has to travel in the seed tube in order to minimize the time the seeds are in the tube. Seed travel through the tube can be slowed to a greater or lesser extent, depending on field surface anomalies which cause the row unit to move, by contact with inner walls of the tube which adversely affects seed spacing. Also to minimize wall contact the seed tubes are generally orientated vertically.
Typically the seed tubes curve rearward near their discharge ends so the horizontal velocity component of the exiting seed closely matches the forward travel speed of the row unit in the range of 4.5-5 mph. This results in the relative horizontal velocity between the seeds and the ground being near zero leaving only a vertical velocity component in order to minimize the tendency of seeds to roll along the furrow after contacting the ground which again adversely affects seed spacing.
In general, these known systems work well under good smooth tilled field conditions and slower planting speeds, typically recommend no more than 4.5 mph. However it is now more common to reduce tillage significantly, and often there is no tillage at all on a field prior to seeding, with the result that field surfaces can be quite rough, since humps and hollows made by traffic harvesting a prior crop are not smoothed out by conventional tillage.
Transferring the seeds effectively and consistently from the singulating meter to the furrow is achieved in U.S. Pat. No. 9,480,199 to Garner et al. by replacing the gravity drop seed tube with a brush conveyor system. Similarly, U.S. Pat. No. 6,681,706 to Sauder, et al uses a paddle belt conveyor system.
U.S. Pat. No. 8,336,471 to Gilstring discloses a singulating meter mounted on a row unit where pressurized air is used to singulate the seeds and then also passes in an air stream through the seed tube carrying the seeds with it. In U.S. Pat. No. 9,137,941 to Stark a singulating meter such as disclosed by Gilstring delivers seeds from the meter through a seed tube to the furrow using a pressurized air stream. The pressurized air reduces the effect of speed variances due to contact with the tube walls since the seeds are being forced along the tube by the air stream. The seeds however exit the seed tube at a much higher speed than the ground speed of the implement and so Stark uses a seed catching member such as a wheel or plate to catch the seed as it leaves the seed tube and press it firmly into the bottom of the furrow to prevent the seed from rolling along the furrow.
Means for preventing such rolling and bouncing of seeds is also described in U.S. Pat. No. 5,918,557 to Schaffert. U.S. Pat. No. 6,666,156 to Mayerle et al. discloses a downward biased seed flap pivotally attached rearward of a vertically oriented seed tube to control seed placement. U.S. Pat. Nos. 4,519,525 to Wunschl et al. and 3,848,552 to Bauman et al., and European Patent Number EP0216057 to Dreyer disclose similar seeders where a seed hopper and a singulating meter are mounted on the tool bar and the singulating meter delivers singulated seeds using pressurized air streams to each of a plurality furrow opener assemblies mounted rearward of the tool bar. These implements provide centralized locations for the singulating meters resulting in less complexity and less costly systems, with more convenience in that there is only one seed hopper to fill and clean out.
Implements such as disclosed by Wunschl and Bauman however require a significantly longer delivery tube to transfer the seeds from the singulating meter to the furrow openers, and these tubes are often bent in numerous locations to accommodate mounting the tubes with the input end at the singulating meter and the output end at one of a number of widely spaced furrow openers. As a result, the seeds experience significantly more contact with the tube walls which adversely affects seed spacing.